1. Technical Field
The invention relates to a method of introducing and removing workpieces, particularly vehicle bodies, into or out of a tank or a treatment booth, whereby the workpieces inside the tank are treated either in a gaseous environment such as being coated with powder or wet paint, or the tank is a dip tank filled with a liquid medium suitable for the surface treatment of the workpieces. The invention also relates to an apparatus for the surface treatment of workpieces and to a system for the surface treatment of vehicle bodies.
In the subject matter according to the invention, the workpieces or vehicle bodies are continuously moved in a translational manner toward a treatment area such as a treatment bath, a treatment booth etc. and are transported to and from the treatment area while maintaining this movement.
2. Prior Art
Devices for the surface treatment of one or more vehicle bodies are generally divided into continuous and non-continuous conveyors.
In the case of non-continuous conveyors, so-called cyclical systems, the vehicle bodies on object supports are sequentially transported over successively arranged dip tanks where they are stopped. Lifting or rotating devices are used to dip the vehicle bodies into a bath medium suitable for surface treatment and located in the dip tank, and the vehicle bodies are lifted out again once the process time is over. These systems manage without inlet and discharge areas, allowing the treatment bath dip tanks to be shorter than in the case of continuous conveyors. These systems can only be used, however, at small production rates because system capacity depends on the desired process time and is therefore considerably restricted. The application range of such systems is consequently limited.
A rotating device for cyclically operating systems is known from DE 43 04 145 C1 which discloses a rotating device securely mounted above a dip tank and to which at least one vehicle body can be secured. Rotation through approximately 180xc2x0 of the rotating device causes a vehicle body to be dipped into a treatment bath and a further rotation causes it to be guided out.
In the case of continuously conveying systems, vehicle bodies are continuously transported along the aligned treatment baths and are guided into and out of the treatment bath using lowering and raising means into and out of the bath medium. Due to the continuous conveyance of these systems, a treatment bath""s inlet and outlet areas have to be designed at an angle. Each dip tank therefore requires a longer inlet and discharge area, which causes a dip tank and hence the entire system to be considerably extended. The known lowering means likewise do not ensure that air pockets remain in the workpieces dipped in the treatment bath. Due to cavities entailed by the structural design, this problem arises to an extreme degree particularly when vehicle bodies are dipped into the treatment bath. In the prior art, additional steps are therefore absolutely essential in order to reduce air pockets. It is for example proposed in GB 1 434 348 to move to and fro a lowered vehicle body that is dipped into the treatment bath.
A continuous conveyor for guiding workpieces in galvanic metallization and chromium-plating plants is known from German published document DE-AS 25 12 762. The system known from this document relates to a revolving conveyor device that continuously transports the workpiece to be treated. When the conveyor device rotates, the workpieces are each automatically dipped into a tank, guided underneath it while continuing the movement, moved out of the tank and again dipped into the next tank. Various options are mentioned in order to cause the workpieces to be dipped in or lifted out.
On the one hand, workpiece holders are rotatable by cams or by ramps and surfaces that extend downwards at an angle. When such a workpiece holder continues to move, however, only the rotation is initiated, the further rotational process takes place in an uncontrolled manner merely under the influence of gravity. Such a device suffers from the drawback that heavier workpieces fall into a treatment bath in an uncontrolled manner, which is totally unsuitable for larger, much heavier and more sensitive workpieces such as vehicle bodies. The system described therein also specifically focuses upon a design having current carrying means which simultaneously serve as an actuator for initiating a workpiece holder""s rotation. The rotational process which is uncontrolled and hence indefinite in terms of time and place also makes it impossible to minimize the individual dip tanks"" inlet and outlet areas. The system disclosed therein does not aim thereat either.
Finally, a container rotation device is known from German published document DE-OS 29 01 027; in this device, containers., preferably bottle containers, are intended to be rotated automatically and without manual action. The device comprises conveyance means, drivers that are rotatably supported in a mount, and a curved control surface which controls the drivers such that they secure the containers. chain wheels connected to the drivers engage with gear teeth.
The arrangement is such that the chain wheels, drivers and containers are rotated as a result of engagement with the teeth. Only the rotation by means of chain wheels is disclosed in the device shown therein. The container is also intended to be rotated only in order that various container parts are more effectively accessible. An insertion or removal process as a result of rotation is neither depicted nor in any way implied.
Technical Problem
The technical problem upon which the invention is based is to provide a method and an apparatus for the surface treatment of workpieces, in which on the one hand the treatment areas can be minimized in terms of their dimensions, while on the other hand, high production rates can also be achieved.
Solution of the Technical Problem
This technical problem is solved by a method of introducing and removing workpieces, particularly vehicle bodies, into and out of a treatment area suitable for the surface treatment of said workpieces, wherein said work pieces are detachably secured on mounting frames which each have a rotary axis vertically aligned in relation to the direction of movement of said workpieces, said rotary axes are continuously moved translationally and at a constant speed, and said workpieces at the start and at the end of said treatment area are simultaneously rotated through about 180xc2x0 around one of these rotary axes in a controlled and always guided manner in the direction of the translational movement.
An apparatus solving the above technical problem for the surface treatment of workpieces in treatment for baths or treatment booths, particularly for the surface treatment of vehicle bodies, comprises at least one mounting frame for receiving one or more workpieces, said frame being continuously moveable along a direction of movement of said workpieces predetermined by the arrangement of said treatment bath or said booth, having receiving means with which said workpiece can be detachably fitted to said mounting frame, and having a rotary axis disposed across the direction of movement, actuating means for rotationally shifting said mounting frame around its rotary axis, said actuating means and said mounting frame being constantly coupled together during the process of rotation so that the rotation is always controlled and guided, guidance means with which said mounting frame can be guided in the direction of movement, and drive means with which said mounting frame is continuously moveable in the direction of movement.
The technical problem is also solved by a system for the surface treatment of vehicle bodies comprising a plurality of successively arranged treatment baths, a supply means for supplying said vehicle bodies individually in an inlet area, a device for the surface treatment of workpieces in said treatment baths, particularly for the surface treatment of vehicle bodies, with at least one mounting frame for receiving one or more workpieces, said frame being continuously moveable along a direction of movement of said workpieces predetermined by the arrangement of said treatment bath or said booth, having receiving means with which said workpieces can be detachably fitted to said mounting frame, and having a rotary axis disposed across the direction of movement, actuating means for rotationally shifting said mounting frame around its rotary axis, said actuating means and said mounting frame being constantly coupled together during the process of rotation so that the rotation is always controlled and guided, guidance means with which said mounting frame can be guide in the direction of movement, and drive means with which said mounting frame is continuously moveable in the direction of movement, wherein said plurality of spaced apart mounting frames is continuously moved above said plurality of successively arranged treatment baths, wherein the vehicle bodies are individually supplied in said inlet area by said supply means in accordance with the movement speed of said mounting frames, and wherein in an outlet area of said system, the now treated vehicle bodies are detached and can be removed, from said mounting frames by detachment means while continuously moving said frames.
Such a system is also usable in connection with treatment booths instead of treatment baths.
The invention is based on the idea of rotating the workpieces to be introduced into the treatment areas, during a continuous movement of these workpieces, at the boundary area of a treatment area at the same time as a controlled and completely guided rotational movement around a rotary axis across the workpieces"" continuous direction of movement. As a result of this first ever co-ordination of the workpieces"" continuous movement along the treatment areas and the simultaneous completely guided rotational movement thereof around the rotary axis located across the direction of conveyance, the workpieces, particularly vehicle bodies, can be rotated into and out of a treatment area with such accuracy that the inlet and outlet areas of each treatment area can be provided with vertical or almost vertical end walls. The length of each individual treatment area can therefore be reduced to a minimum. At the same time, this minimizes the total length of a system that has a plurality of successively arranged treatment areas and particularly a number of treatment baths arranged in a row. This reduction is about 20% for a capacity of one hundred vehicle bodies per hour compared to conventional continuous conveying systems. The advantages of a continuous conveying system are therefore combined for the first time with a rotational device""s benefits as known from the prior art.
In the case of a treatment bath composed of a liquid medium, air bubbles are largely avoided by the rotational process while the workpieces are being dipped. Even if the workpiece is dipped, the air pockets that may have been caused by the treatment process can also be reduced, however, by moving further the workpiece in the treatment bath. In addition, occlusions of dirt on horizontal surfaces are reduced because the vehicle bodies are rotated above and within the bath.
In the method according to the invention, all that has to be provided is a minimum safety gap between the workpiece to be introduced into the treatment area and the end walls of the treatment area or dip tank. To ensure a minimum total length of the treatment area, the rotational speed and speed of movement then have to be coordinated with one another, by taking the safety gap into consideration, such that after completion of the rotational process, while observing the safety gap, the front section of the workpiece is positioned at the first end wall and is positioned at the second end wall during the process of removal by rotation. In the prior art, this minimum safety gap has to be much larger, as for example in the chromium-plating system known in the prior art and in which a completely uncontrolled process of insertion by rotation occurs. By coordinating the speed of the translational movement and the speed of rotating the workpiece in and out, the workpiece""s movement curve can be accurately predetermined and adapted to the shape of the treatment area to an optimum degree. The total length can therefore be kept to a minimum as well.
By keeping the rotational speed essentially constant, a steady movement curve can be achieved, which is particularly important in the case of heavier workpieces so as to achieve an even process of rotation in and out, because greater forces which do not permit an accurate movement sequence otherwise take effect when there are changes in angular velocity. For example when the heavy vehicle bodies placed on a mounting frame temporarily move further than desired during rotation in and out due to inertia when there is a change in angular velocity.
The procedure according to the invention can be used for a wide variety of surface treatment techniques. For instance, the introduction and removal of workpieces into and out of a liquid medium is perfectly suited to performing dip coating. The procedure according to the invention is also, however, very well suited to powder coating or wet paint application. As with the treatment tanks needed for dip coating, the treatment booths envisaged for this purpose raise the problem of guiding the workpieces in and out of an inlet and outlet area of the booths. In consequence, these booths may be located above or below the workpieces"" supply level.
Finally, the linking, according to the invention, of a continuous translational movement and a controlled and constantly guided rotary movement of the workpieces is also suitable for preventing the formation of fat edges in a dryer when workpieces have already been coated. For this purpose, instead of a gap between the rotary axis and the workpiece, the workpiece should be optimally arranged close to the rotary axis or even within the area of the rotary axis in the surface treatment apparatus according to the invention.
A mechanically very simply structured and low-maintenance design is obtained by providing the mounting frame with at least one laterally attached lever which interacts with a guide in order to cause the mounting frame to rotate. By adapting the lever length, heavy workpieces can also by rotated on a mounting frame in a very easily controlled manner.
Attaching at least one lever on opposite sides of a mounting framexe2x80x94whereby these opposite levers are counterrotated by a predetermined angular amountxe2x80x94for the first time ensures that if the guidance devices are correspondingly designed, the mounting frame is always supported both in the forward direction and in the reverse direction in relation to the rotational direction and is therefore also accurately guided.
This effect can also be improved when two levers are disposed on each side of the mounting frame; these levers are each disposed on one side of the mounting frame symmetrical to the rotary axis and lever configurations on the opposite sides are rotated through 90xc2x0.
A very simple embodiment of the actuation means is obtained by designing it as a directional rail.
By providing guide surfaces on the directional rails in the inlet and outlet area of a treatment bath, i.e. in the boundary area, the rotation can be brought about by simply sliding corresponding devices up and down on the mounting frame or by rolling them off the frame.
Rotation is best controlled by upwardly or downwardly tilted guide portions which are inexpensive and easy to manufacture as a result of designing the individual guide portions to be simple and straight.
The individual guide portions are best tilted downwards through about 45xc2x0, other guide portions are tilted upwards through about 45xc2x0.
A low-friction and easy-maintenance design is obtained in that rollers which interact with the directional rails are disposed at the lever ends.
More complex, albeit extremely accurate actuation devices which can even be used with the heaviest of items comprise toothed racks or screw spindles securely attached to the treatment bath and which interact with gear wheels or worm gears correspondingly formed on the mounting frame.
This also makes it possible to insert intermediate gears if need be.
In the area of the rotary axis, the mounting frame advantageously comprises guide means which are guided in the guide rails. This brings about the continuous translational movement with utmost accuracy on to the mounting frame in the direction predetermined by the guide rails.
Rollers are particularly provided as guide means in the guide rails because the friction is therefore minimized, which is important in the case of several sequentially arranged mounting frames connected together.
By arranging receivers on the mounting frame, workpieces can be secured thereon in a directly detachable manner, or indirectly for example in the case of vehicle bodies that are detachably secured on a skid.
By having the receivers assume a position that remains unaltered in the movement of direction with respect to a vertical direction during the mounting frame""s translational movement, it is extremely simple to mount a vehicle body using a skid by way of adjacent conveying means located at the same height.
All the drive means known from the prior art can be used for the continuous movement of the individual workpieces. In particular, chain drives, traction rope arrangements, threaded rods or self-propelled mounting frames that have their own drive are perfectly suitable.
The angle data given in this application should not be regarded as absolute values. Values that deviate by xc2x110% are also covered by the disclosure.